DE3414294A1 - SAFETY VALVE FOR LIQUID GAS TANKS, ESPECIALLY SHIP TANKS - Google Patents

Description

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34H29A

Applicant: Dipl.-Ing. Drago KOBER in 5020 Frechen-Bachem and Dipl.-Ing. Erich MARTIN in 5047 Wesseling

Designation: Safety valve for liquid gas tanks, especially ship tanks.

The invention relates to a safety valve for liquid gas tanks, in particular ship tanks, with a pilot valve with a predetermined set pressure and with a main valve controlled by this pilot valve, the one on the tank side Inlet that merges into a valve seat, a side outlet, one connected to the pilot valve Pressure chamber and a valve part, in particular a piston, which

a. on the inlet side of the gas pressure in the tank and on the side of the pressure chamber via the pilot valve with one of the Piston is applied against its valve seat pressing pressure and

b. when a response pressure in the tank is exceeded, it disengages from its valve seat and the connection releases between inlet and outlet.

Such safety valves are, for example, from DE-PS 27 31 804 or the brochure on AGCO safety valves the series 95 known. In these safety valves, the main valve has a piston with an O-ring seat. Of the Tank pressure is fed into the pressure or dome space on the top of the piston via the pilot valve. The one to the inlet The lower piston surface facing the main valve is acted upon directly by the tank pressure. The latter is smaller than that upper, so that the piston is pushed down and the

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Valve is closed. If the tank pressure increases and it reaches the setting pressure of the pilot valve, the pilot valve opens and vents the pressure space above the piston. As a result, the force acting from below is now on the piston larger, the main valve opens. If the tank pressure drops to the closing pressure of the pilot valve, the pilot valve closes and the tank pressure acts again on the upper piston surface, whereby the main valve also closes.

Based on IMO regulations A 328 (IX) Chapter XV (XV.1) Liquefied gas tanks of gas tankers may only be filled to the extent that the cargo is at the response pressure of the safety valve occupies no more than 98% of the geometric tank volume, even if a reflux system or a System for keeping the pressure constant is provided. In the case of pressure tankers, for example full-pressure or semi-pressure tankers, consequently, the maximum permissible filling rate can only be achieved when taking over frozen food LPG the saturation pressure immediately after charging has the same value as the response pressure of the safety valve. If, for example, the saturation pressure is only 1 bar immediately after charging (butane, density = 0.594), so the maximum possible filling rate of 98% is not achieved, because according to IMO the tank may only be filled so far that it at 5.5 bar (butane, density = 0.52) maximum, i.e. 98% full. This will cause the tank to overfill when heated the charge prevented, for example, in the event of a fire. The expansion due to the supply of heat in normal operation, in particular Heat radiation or heat conduction is avoided by the aforementioned reflux system. The limitation of the Depending on the type of liquefied gas, the filling rate can mean a loss of filling rate of up to 15%.

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In the previously known safety valve from AGCO, model 95, a so-called safety valve is used to avoid this disadvantage Auxiliary pilot provided. This is placed on top of the primary pressure setting of the pilot valve. It several auxiliary pilots can also be placed on top of each other. The auxiliary pilot contains like the primary pressure setting a helical spring, the spring force of which essentially determines the setting pressure of the pilot valve. In this way the pilot valve can be adjusted to the physical parameters of the Charge can be adjusted, whereby the safety valve then responds at higher pressures. This solution with However, the auxiliary pilot has the disadvantage of being unwieldy. Due to its pressure-determining helical spring is a Auxiliary pilot only suitable for a very narrow pressure range, so a graduated number of auxiliary pilots must to be available in order to set the possible pressures between one bar and the maximum admissible pressure of the tank to be able to cover. When taking over a load, the auxiliary pilots of the individual tanks usually have to be replaced The new auxiliary pilots to be deployed must correspond to the saturation pressure of the liquefied gas taken over to be selected. Assembly work is necessary, the auxiliary pilot is connected to the primary via several screws Pressure setting of the pilot valve connected. Finally, when replacing auxiliary pilots, errors can occur, if an auxiliary pilot with an incorrect pressure value is used by mistake, in particular due to a reading error or smaller particles of matter, especially dirt, will fall into the primary pressure setting.

Proceeding from this, it is the object of the invention to avoid the disadvantages of the known safety valve and that

known safety valve of the type mentioned to the effect that a convenient setting of the Pilot valve is possible without having to deviate from the standard regulations.

Based on the known safety valve of the type mentioned above, this task is carried out by an additional, so released second pilot valve, which is connected in parallel to the first pilot valve, a manually operated, continuously has adjustable setting device for the set pressure and to pressure values below the set pressure of the first pilot valve is adjustable.

With this safety valve, in contrast to the previously known safety valve, the one for the maximum permissible Tank pressure designed first pilot valve does not change, which also eliminates the risk that during assembly faults on the first pilot valve are caused by auxiliary pilots. Through the second pilot valve connected in parallel, preferably continuously in the entire pressure range between atmospheric pressure and the maximum allowable pressure of the tank is adjustable, there is no need for storage, control and handling of many, graduated Auxiliary pilots. At the same time, the optimal one can always be used Pressure value can be set on the second pilot valve, in the case of the previously known solution, however, one is on the respective instructed existing auxiliary pilots. Their set pressure does not necessarily fall with the optimum set pressure for the charged liquefied petroleum gas together.

Instead of being designed as a piston, the valve part can also be designed as a membrane or bellows. The manually operated continuously adjustable adjustment device can be equipped with an auxiliary system, for example a pneumatic auxiliary system.

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be prepared, but it can work without auxiliary energy and only use the tank pressure. The adjustment device can act directly on the valve element of the second pilot valve, this second pilot valve on the other hand, it can also consist of a pressure measuring and switching device and a valve controlled by this.

In a preferred development, the second pilot valve has a manometer that shows the respective tank pressure and also a switching process at an adjustable pressure value triggers. As a result, reading errors are additionally reduced and transmission and setting errors are largely reduced suppressed. After completion of the charging process, the saturation pressure of the charged liquid gas can be measured on the pressure gauge can be read, on the adjustable pressure switch device of the manometer, the set pressure of the second Pilot valve can be adjusted without the risk that this setting pressure is below the saturation pressure of the accepted charge.

In another preferred development, the second pilot valve is in series with one at an elevated temperature automatically opening valve switched. This means that the second pilot valve can only control the main valve when if the valve is preferably equipped with a fuse after the fuse has been destroyed opens. In normal operation, with an intact fuse, the second pilot valve has no influence on the main valve. In accordance with the IMO regulations, Section 8.3, this provides an opportunity to prevent the loss described above Turning off the charge rate, realized. According to these regulations, a safety valve must also be installed in addition to a jerk loss system which is activated in the event of fire and at a lower pressure in comparison responds to that of the normal safety valve.

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Further advantages and features of the invention emerge from the remaining claims and the description that follows of non-restrictive exemplary embodiments, which are described below with reference to the Drawing will be explained in more detail. In the drawing show:

1 shows a schematic representation of a safety valve with a main valve and two connected in parallel Pilot valves,

2 shows a schematic representation similar to FIG. 1, but with a different design of the second pilot valve, and

3 shows a representation similar to FIG. 1, but with an additional valve which, when a fuse breaks opens and is connected in series with the second pilot valve.

The safety valve for liquid gas tanks consists essentially of a main valve 20, a first, lead-sealed Pilot valve 22 and a second, continuously adjustable pilot valve 24, which are connected in parallel and both control the main valve 20 independently of one another. In a known manner, the main valve 20 has a tank-side Inlet 26, which merges into a valve seat 28 towards the top. This is a valve part designed as a piston 30 assigned. This piston 30 is therefore acted upon from below by the tank pressure prevailing in the inlet 26. The main valve 20 also has a side outlet 32 which communicates with the inlet 26 when the Piston 30 is lifted from its valve seat 28. Above the piston 30 there is a pressure chamber 34, also a dome chamber called, which is connected to the two pilot valves 22, 24 via a control line 36.

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Via an impulse line 38 in which a check valve 40 and then a diaphragm 42 are arranged one behind the other, the pressure chamber 34 and thus the upper bottle of the piston 30 are acted upon by the tank pressure prevailing at the inlet 26. Because the upper piston area is larger ^! "As the effective lower piston area facing inlet 26, main valve 20 is normally closed.

The main valve 20 opens when the pressure chamber 34 is vented more than gas directly via the orifice 42 can flow from inlet 26. This connection of the pressure chamber 34 with the outside atmosphere takes place via at least one one of the two normally closed pilot valves 22, 24.

The pilot valves 22, 24 are shown schematically in the figures in order to explain their function more clearly can. The actual structure can be seen, for example, from the above-mentioned brochure for the AGCO safety valve Series 95. The first pilot valve 22 shown on the left in the figures has an inlet pointing downwards 44, which merges into a valve seat ". Normally, a stem-shaped valve part 46 rests on this in a sealing manner. An outlet 48 is connected to the outlet 32 via a line. Inlet 44 and outlet 48 open into a lower one Pressure space which is closed at the top by a first membrane 50. Located above this first membrane an upper pressure chamber of the pilot valve 22, which is bounded at the top by a larger, second membrane 52 and Via a line 54 which opens into the pulse line 38 between the check valve 40 and the diaphragm 42, with gas below Tank pressure is applied. The valve part 46 is connected to the two membranes 50, 52 and is at its upper

The end is loaded by a compression spring 56. This is to a certain set pressure by means of an adjustment device shown 58 set and sealed with a lead seal 60.

In: "The two pressure chambers of the first pilot valve 22 are normally tank pressure. This tank pressure is sufficient to compress the compression spring 56, the valve part 46 can move away from its seat, thereby becoming the lower pressure chamber of the pilot valve 22 and thus the pressure chamber 34 of the main valve 20 practically free of pressure, since the The amount of gas flowing in directly from the tank through the diaphragm 42 is not sufficient to build up a pressure. In case of falling the pressure in the pressure chamber 34, the piston 30 is moved upwards, so that the path from the inlet 26 to the outlet 32 is free is. The first pilot valve 22 closes again when the tank pressure is no longer sufficient to compress the compression spring 56. Then pressure can build up again in pressure chamber 34, and the main valve closes.

In the embodiment of Figure 1 is for the purpose of a particularly simple explanation of the invention, the second pilot valve 24 as far as possible coincides with that first pilot valve 22 is formed. Corresponding reference numbers are provided with a prime. So are the two of them Inlets 44, 44 ', the two outlets 48, 48' and the two upper pressure chambers connected to each other via lines. Instead of the permanently set, lead-sealed compression spring 56 however, a weaker helical spring 62 is provided, which is controlled via a manually operated adjusting device 64 can be adjusted with scale 68. As a result, the set pressure of the second pilot valve 24 can be screwed in the adjustment screw designed as a set screw with a handle

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Device 6 4 between normal pressure and, with maximum screwing in, set the set pressure of the first pilot valve 22. The set pressure can be read on the scale 68,

There is also a test and adjustment device in each of the figures shown. For this purpose, nitrogen from a nitrogen bottle 70 is fed into the control line 36 via a valve 68 fed in. The gas flowing out of the nitrogen bottle 70 It first passes through a pressure reducing valve with a flow meter 72, before it passes via a line 74 to the valve 68 flows. The pressure prevailing in line 74 can be read off via a manometer 76.

In Figure 2, an improved practical embodiment for the formation of the second pilot valve 24 is shown, which other parts are identical. The tank pressure prevailing in the impulse line 38 in front of the diaphragm 42 is controlled by means of a displayed as a Bourdon tube 78 designed spiral spring for the pressure measurement, the display takes place in a known manner by means of a pointer 80 which is provided with a switching flag 82. This occurs when compared to the representation increasing Pressure between two nozzles 84 and 86 and then blocks that maintained between these two nozzles 84, 86 Gas flow. The lower nozzle is a jet nozzle 84 and is supplied with compressed air via an instrument air supply. This compressed air is fed in from a source (not shown) at 88 and reduced in a pressure reducer 90 and then passes through a check valve 92. Above this check valve, there is an emergency supply 94, which consists of a pressurized gas cylinder and a pressure reducing valve, provides an emergency supply in the event of failure the instrument air supply.

The upper nozzle is a catch nozzle 86 which is aligned with the jet nozzle 84 and which is directly connected to a pressure chamber of a Control valve 96 is connected, which in turn performs the actual function of the second pilot valve 24, in In contrast to the exemplary embodiment according to FIG. 1, however, it is controlled by the pressure switch device just described will.

The two nozzles 84, 86 are designed as positioning pointers Adjusting device 64 attached and adjustable by setting this setting pointer to any pressure values. The control valve 96 also has a lower, small-area membrane 98 designed as a bellows a large-area upper membrane 100, both membranes 98, 100 are connected to one another via a valve part 102, the In the illustration of FIG. 2, an output 104 of the control valve 96 blocks. At the inlet 106 of the control valve 96, the lower chamber of which is constructed essentially similarly like the lower chamber of the first pilot valve 22, the control line 36 is applied.

If the pressure in the impulse line 38 increases compared to the illustration, the pointer 80 moves further to the right and interrupts the gas flow between the two nozzles 84, 86 with its switching flag 82. The pressure builds up as a result in the uppermost .Druckraum of the control valve 96, the pressure prevailing in the control line 36 is now sufficient to the Lift valve part 102 from its seat so that the connection of the control line 36 to the outside atmosphere is free. As a result, the processes already described with reference to FIG. 1 take place, in particular the main valve opens 20th

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The embodiment shown in Figure 2 is only intended as an accessory; game be other pressure switching means instead of the \ arrangement shown with switching plate 82 and nozzles 84, 86 are possible.

Finally, the embodiment according to FIG. 3 corresponds largely the embodiment of Figure 1, but with the exception that in the leading to the second pilot valve 24 An additional valve 108 is inserted into the control line 36, which under the action of a fuse 110 normally closed. Because of this series connection, the pressure in the control line 36 can only increase then relax via the second pilot valve 24 if the ..... fuse 110 due to fire or other high temperatures is destroyed, whereby the additional valve 108 is opened and the path to the inlet 44 'of the second pilot valve 24 releases. If the fuse is destroyed, the conditions are as explained with reference to FIG were, when the fuse 110 has blown, the circuit according to FIG. 3 corresponds exactly to the circuit according to Figure 1.

The additional valve 108 can also be behind the second pilot valve 24, that is to say between its outlet 48 'and the outlet 32 to be on. Furthermore, the additional valve 108 can be in the part of the control line leading to the control valve 96 36 can be inserted in the exemplary embodiment according to FIG.

The additional valve 108 with the fuse 110 is constructed in a manner known per se: The path from an inlet 112 to an outlet 114 is normally blocked by a valve part 116, which is mechanically operated via the fuse 110 is pressed against its valve seat. The contact

pressure is set by a screw to such an extent that the Auxiliary valve 108 is normally closed. The fuse 110 thus transmits the control pressure of the Screw 118 on the valve part 116. The fuse 11Oi is a rod made of a material that, for example has a melting point between 89 and 104 degrees Celsius. If a fire breaks out, this material melts, so that the mechanically rigid connection between the screw 118 and the valve part 116 is omitted. A spring 120 then pulls the valve part 116 in the release position, whereby the additional valve 108 is opened.

Other designs of the additional valve, for example the design according to DE-PS 27 31 804, are also possible. Instead of the fuse 110, other releasable devices can also be used which, through the action of temperature, Remote control or manual control can be triggered and optionally specified in addition to the fuse 110 are.

In the case of the safety valve with two pilot valves, the additional valve 108 ensures that there is a brief pressure increase no gas is blown off. Such increases in pressure can occur, for example, when charging or when driving in heavy seas occur. In the safety valves according to FIGS. 1 and 2, the main valve 20 always opens when the second pilot valve 24 opens. As a result, however, gas flows into the open, at least this is not permitted in the port and moreover means a loss of charge. The second pilot valve 24 is now normally opened by the additional valve 108 disabled, the second pilot valve 24 only comes into effect in the event of a fire outbreak.

Claims (6)

Expectations Safety valve for liquid gas tanks, in particular ship tanks, with a pilot valve (22) with a predetermined Set pressure and with a main valve (20) controlled by this pilot valve (22), the one tank-side inlet (26) which merges into a valve seat (28), a side outlet (32), one with the Pilot valve (22) has connected pressure chamber (34) and a valve part, in particular a piston (30), the a. on the inlet side of the gas pressure in the tank and on the side of the pressure chamber (34) via the pilot valve (22) is acted upon by a pressure which presses the piston (30) against its valve seat (28) will and b. comes out of engagement with its valve seat (28) when a response pressure in the tank is exceeded and the connection between inlet (26) and outlet. (32) releases, characterized by a second pilot valve (24) which - is connected in parallel to the first pilot valve (22), - A manually operable, continuously adjustable setting device (64) for the set pressure has and - Can be set to pressure values below the set pressure of the first pilot valve (22). 2. Safety valve according to claim 1, characterized in that the adjusting device of the second Pilot valve (24) between the normal pressure and the set pressure of the first, lead-sealed pilot valve (22) is adjustable. 3. Safety valve according to claim 1, characterized in that in series with the second pilot valve (24) an additional valve (108) is arranged, which has a fuse (110), normally closed and opens automatically if the fuse (110) is destroyed. 4. Safety valve according to one of claims 1 to 3, characterized in that the second pilot valve (24) has a pressure scale with pointer (80). 5. Safety valve according to one of claims 1 to 4, characterized in that the second pilot valve (24) has a pressure display and switching device, in particular a Bourdon tube (78), a membrane or a bellows, which is connected to a control line (26) and that preferably a pointer (80) with a Switching flag (82) and a pressurized jet nozzle (84) and a collecting nozzle (86) associated therewith are provided. 6. Safety valve according to claim 5, characterized in that it further has a control valve (96) Has pressure gain.